I have always loved this story and it has been one of my favourites of all time. The only problem with it (even when I saw it as a child) was not enough daleks.
An epic invasion looks a bit rough with only 3 daleks available, no matter how many camera angles you use! I was a bit worried that adding new sfx to the story would look out of place and be glaringly obvious.
Happily though, the special edition was obviously put together by someone after my own heart. The new CGI (and a few new short live action scenes)blend in really well with the original footage and keeps to the same style. It is not too OTT, but does give a better sense of scale. The quality of the transfer is good, so it looks good even on a big telly.
So there are more daleks, more Ogrons and better lasers. This really appealed to my inner 10 year old!